1. Field of the Invention
The present invention is related to an image forming apparatus such as a copying machine, a printer, a facsimile, or the like.
2. Related Art
The image forming apparatus includes apparatus main body, and a document conveyance apparatus or image reading means (for example, a scanner unit) disposed on an upper side of the apparatus main body. A document set in the document conveyance apparatus, or a document disposed on the scanner unit is optically read by the scanner unit.
An image forming apparatus that uses an electrophotographic process pre-charges a photosensitive drum contained in the image forming means, irradiates light onto the surface of the photosensitive drum to thereby form an electrostatic latent image, develops a toner image with a developing device, transfers the toner image with a transfer unit onto a recording material, fixes the toner image onto the recording material with a fixing unit, and thereby forms an image on the recording material.
The high-weight scanner unit is housed in the housing body. An image reading apparatus has been proposed that includes an opening/closing moveable configuration from a position at which the housing body is closed to an open position at which the inner portion of the apparatus main body is visible. A structure is disclosed in which consumable products such as toner containers, or the like, disposed in an inner portion of the image forming apparatus are configured in an attachable/detachable state by moving the housing body between an open and a closed position.
However, the opening and closing operation of the housing body described above is assisted by an assist spring in order to improve the operation performance of a user. The assist spring includes for example a torsion coil spring. However, the set load of a torsion coil spring is extremely large, and therefore makes assembly performance problematic.
In this regard, the assembly performance can be improved by using a tension spring as an assist spring to produce a return force to restore the free length when compressed by pulling in a longitudinal direction.
However, when the rotation angle in the housing body is large, a tension spring that has a high allowable stress to resist fatigue by cyclic stress must be provided, and therefore manufacturing costs were increased.